930 transmission

[Robert Sanchez]

I recently bought a 1988 930 euro with a 4 speed tranny. What do I need to do to install a G-50 5- speed?
Thanks for the info
Bob

[RickM]

Bob, Check here...I believe the same general info applies:

OK, all you 3.6 guys. Why not a G50 too

[Robert Sanchez]

Rick, thanks for responding, I find the 4 speed very high geared and not frendly for city driving. It would be nicer to have a 5 speed. Would the 915 work with 400+ HP of my 930?
Bob

[magilla]

Nope. I think 300 is about the max for a 915.

[beepbeep]

1. There's nothing wrong with 4-speed.
2. G50 means cutting the bellhousing ($$) or reworking the firewall ($$) and converting to coilovers ($)
3. 915 can take lot's of power (if you keep the temps down) but it cannot take lot's of torque...that's why it's wrong to say it can handle max 300HP...it can probably handle 1000HP if you can keep the torque down by high gearing and engine that revs to 20000RPM... Most hot rodders say 915 cannot survive 930 torque for prolonged periods. I bet Hayden can explain this quite nicely.
4. There are lower R&P sets for 930 tranny, they help
5. G50 is nice but costly

[Bailey]

I am having race gears installed in my 86 930. Should be better on the track and maybe friendlier around town. I'll only be able to go 140 mph now instead of 170 and will miss that top speed since I get there so often .

[David]

I think you'd need at least $5000 in parts and a few thousand more in labor if you don't have acess to a machine shop and welding equipment.

On the other hand a ring & pinion to lower the overall gearing is about $1500 plus labor.

[eddiec]

Will someone explain to me the problem with the 4 speed in the 930.
In my car, 1st gear gets me moving up to about 40mph (high revs are in use for this), 2nd is weak at low rpms, say a slow coast through a turn and is under powered at less than about 3000 rpms. It's a killer from 3500 rpms up and is good to about 80+ mph. 3rd is the same, sort of weak at low rpms but when used at 3500 rpms and up it is a blast. Car runs about 70 mph in 3rd at about 3800 rpms with plenty more where that came from. 4th is good when you want to relax at higher speeds.

For anyone that knows or has one, what improvements are made when the ring & pinion are changed out? I've never riden in or driven a car with this done and I just don't quite understand what is gained.

Thanks!

[turbo6bar]

Eddie, the 930 runs very little compression. When you're off boost, you make very little power. There's little chance second gear can be used for a rolling start, because you just don't have the torque at LOW rpms. The tall gearing works with the turbocharger, but low rpm tractability suffers.

Just my opinion.
Jürgen

[dean]

Originally posted by Robert Sanchez
I recently bought a 1988 930 euro with a 4 speed tranny. What do I need to do to install a G-50 5- speed?
Thanks for the info
Bob

Are you going to do the work or are you going to pay someone?
Dean

[David]

Here's what I understand to be the gearing in the '79 930 (I'm not sure if it changed in other years):



By lowering the ring & pinion gearing, you're not closing the gaps between gears, but the car accelerates better with the shorter gearing so you'd have the impression of a closer ratio transmission.

I think Bruce Anderson wrote about the tall gear ratios the US 930's had comprared to the rest of the world. Besides, with a coefficent of drag probably close to 0.4, I doubt a 400hp 930 could go much over 160 anyway.

Example of lower gearing:

[eddiec]

125 - I think I see. The weak spots at the low rpms are overcome slightly by reaching the power band of the car at a lower speed. Is that how it works? By doing this is the car actually faster? Did you do this to your car? If so, is it something you notice as a big improvement?

Thanks for the grid displays of the different speeds at different rpms using the different gears.

[beepbeep]

125: There is no difference between ROW and US 930 gear ratios.

Here are some curves, much easier to read than Excel spreadsheets:

[Robert Sanchez]

Thanks to you all for your coments, I think the the best way to go would be install a new R&P in my personal situation. Do all the 930īs have 4 gear transmissions?
Bob

[RickM]

4 speed up to '88. From '89 on they went to the G50 variant(s).

FWIW, I think I remember RUF offering a 5 speed for the 930 before '89.

[993.986.]

125 -
If you changed the R&P set, would this require recallibration of the speedometer? If so, what would that entail?

[David]

Beep- I just checked my US manual and I see the gearing is the same as what you list. The only difference I see is that the top speed lower at 155mph and the 0-62mph acceleration is slower at 5.6 sec. I guess this is due to less hp.

I'm still leaning toward the ring & pinion change due to the extreme cost difference to the G50/50. As for the speedometer, I don't what it reads for speed so I don't know if would need to be recalibrated or not.

I know when I changed my 280Z stock 27lb flywheel for an 11lb flywheel it made a big difference in first gear acceleration. I haven't pulled my engine yet so I don't know what flywheel and clutch I have, but I'm planning to go with a Kennedy aluminum clutch and maybe an aluminum flywheel. This may make a big enough change in first gear acceleration to offset some of the first gear acceleration problem. Does anyone have experience with this?

[hilandscott]

The 915 that's mated to the '92 C2 turbo in my SC is shifting just fine and has done its share of tough track days for a number of years now. Perhaps it's the Swepco magic?

I do enjoy the gearing of the 5 speed with the turbo around town and at the track. I've been warned more than once to limit the torque to 300 ft/lbs or so in any 915 application, recommending a tranny cooler for insurance as well.

With the full GHL exhaust, 1 bar spring and large intercooler the C2 engine is making 350-400 ft/lbs.

Perhaps if the engine is in full boost more of the time the transmission might fail. Much of the lifetime of the transmission and clutch (which is Patrick Motorsports) has to do with how it is driven. A smooth on/off throttle (count to three when moving the gas pedal through the range) is recommended for track days. Around town not hitting higher boost levels until third gear-- when the car is at speed and can go somewhere with all that torque-- is also good insurance.

First to second shifts aren't fast with a 915 though, so patience is a part of it.

Enjoy - John

[beepbeep]

125shifter: You probably have standard 930 flywheel with heavy rubber-damped PP. We have one of those in our project car.

We have both OEM 930 3.3 pressure plate and lightweight 3.0 alu PP. These are the weigths:

930 3.3 OEM: 11.75 kg
930 3.x lightweight (not rubber damped): 5.05 kg
930 3.3 OEM rubber clutch disk: 2.17 kg

We don't use 930 flywheel but i guess it weights around 6 kg. As you can see, there is not much that can be earned on flywheel itself. It's original PP and disk that are heavy. If you really want to go bonkers, you can change the flywheel to one of those ultrathin ones and use multiplate clutch with low polar moment of inertia. You see, it's not just weight itself that makes it rev lazy, it's also where the weight is positioned.

Our solution isn't as drastic and we decided to go with 3.0 aluminium perssure plate, lightened flywheel (7kg) and undamped sinered clutch disk. It will keep whole assembly under 13kg

Difference between lightweight and OEM pressure plate (you need modified throwout bearing to use those):

[aseem]

Goran and David, thanks for posting valuable information in tables and graphs. The information needs some clarification however, and I hope that you can help.
First: does the 930 transmisison (say 930/34) have a R&P ratio of 8/38 or 9/38. The two tables differ on this, and I see both numbers here on the PPBBS (I have seen 8/31 as well)
Two: Goran, your table states that first grear has a 2.25 ratio, but the gearing is 16/32=2.0. Should this not be 16/36?

I appreciate any help on this.